The present invention relates to a blood treatment device which collects blood from a patient and a method for blood treatment.
In dialysis treatments, a blood circuit consisting mainly of flexible tubing is used to place the blood of a patient in extracorporeal blood circulation. This blood circuit arrangement includes an arterial blood circuit having an arterial needle at one end to collect the blood from the patient and a venous blood circuit having a venous needle at one end to return the blood to the patient. A dialyzer can be incorporated between the arterial blood circuit and the venous blood circuit.
A roller blood pump is placed in the arterial blood circuit. By driving the pump, the blood of the patient is collected through the arterial needle and flows extracorporeally through the arterial blood circuit, the dialyzer, and the venous blood circuit. There are multiple hollow fibers inside the dialyzer. The blood flows through each hollow fiber.
Two projections are formed on the dialyzer case, one being a dialyzing fluid inlet port and the other being a dialyzing fluid outlet port. Dialyzing fluid of predetermined concentration is supplied in through the dialyzing fluid inlet port, along the outside of the hollow fibers (i.e., between the outside surface of the hollow fibers and the inside surface of the dialyzer case), and then out through the dialyzing fluid outlet port.
The walls of hollow fibers, which contain micropores, form blood purifying membranes. Waste products of the blood passing through the inside of the hollow fibers are dialyzed to the dialyzing fluid through the blood purifying membrane and the purified blood returns to the patient. To remove water from the blood of the patient during the dialysis treatment, the dialysis device includes a ultrafiltration pump.
The amount of water to be removed (water removal rate) is regulated by controlling the driving speed of the ultrafiltration pump. However, if too much water is removed or if water is removed too quickly, the volume of the circulating blood of the patient is excessively reduced such that blood pressure drop or shock may be induced. On the other hand, if the water removal rate is too low, the treatment duration may be prolonged and the burden to the patient can be too great.
Therefore, as disclosed in Japanese laid open patent publication number Hei 11-221275 and Japanese laid open patent publication number 2001-540, there are blood treatment devices that control the rate of water removal while monitoring the condition of the patient. These existing blood treatment devices have used hematocrit values and other blood parameters to monitor the condition of a patient's blood. The hematocrit value is an indicator of blood concentration, and is expressed as the ratio of red blood cell volume to whole blood volume.
The aforementioned blood treatment devices measure the hematocrit value of the patient in real-time when the patient is undergoing water removal, and can control the water removal rate based on the hematocrit value. This control prevents the drop in blood pressure or the shock caused by excessive reduction in the patient's blood volume. More particularly, numerous zones for hematocrit values are set beforehand and the rate of water removal is controlled according to the zone in which the measured hematocrit value belongs.
Although numerous zones were set beforehand for hematocrit values in the aforementioned conventional blood treatment devices and the rate of water removal was controlled according to the zone in which the measured hematocrit value belonged, the zone setting was not necessarily suitable for the individual patient and it was possible that some patients could experience complications.
Individual patients have different hematocrit values at which the patient feels ill, and it is impossible to set a standard hematocrit value for all patients. Therefore, the water removal rate suitable for one patient may not be suitable for another patient who feels ill at that particular rate. Furthermore, the aforementioned conventional technologies not only control the water removal rate, but also other blood treatments such as fluid substitution. Similarly, these other blood treatments may also be unsuitable for all patients.